Desensitizers in unfogged silver halide systems

ABSTRACT

THIS INVENTION RELATES TO IMPROVED SILVER HALIDE SYSTEMS WHICH CONTAIN UNFOGGED SILVER HALIDE GRAINS HAVING METAL DOPANTS OCCLUDED THEREIN AND AT LEAST ONE COMPOUND HAVING A CATHRODIC HALFWAVE POTENTIAL MORE POSITIVE THAN-1.0 WHICH IS A DESENSITIZER FOR SURFACE-SENSITIZED SILVER HALIDE EMULSIONS. IN ONE ASPECT, THIS INVENTION RELATES TO A PROCESS FOR FORMING NEGATIVE PHOTOGRAPHIC IMAGES COMPRISING (1) IMAGEWISE-EXPOSING A SILVER HALIDE EMULSION WHICH COMPRISES SILVER HALIDE GRAINS CONTAINING METAL DOPANTS OCCLUDED THEREIN AND WHEREIN SAID GRAINS HAVE ADSORBED TO THE SURFACE THEREOF A DESENSITIZER OR AN ELECTRON-ACCEPTOR COMPOUND AND (2) DEVELOPING SAID EXPOSED EMULSION IN AN INTERNAL-IMAGE SILVER HALIDE DEVELOPER. BLACK-AND-WHITE AND COLOR DIFFUSION TRANSFER PHOTOGRAPHIC ELMENTS EMPLOYING THE NOVEL SILVER HALIDE EMULSIONS ARE ALSO DESCRIBED.

United States Patent Office 3,687,676 Patented Aug. 29, 1972 3,687,676 DESENSITIZERS IN UNFOGGED SILVER HALIDE SYSTEMS John Spence, Honeoye Falls, Paul Brewster Gilman, Jr., Rochester, and Cynthia Geer Ulbing, Fairport, N.Y., assignors to Eastman Kodak Company, Rochester, NY. No Drawing. Filed July 20, 1970, Ser. No. 56,701

Int. Cl. G03c 1/28 U.S. Cl. 96-108 16 Claims ABSTRACT OF THE DISCLOSURE This invention relates to improved silver halide systems which contain unfogged silver halide grains having metal dopants occluded therein and at least one compound having a cathodic halfwave potential more positive than 1.0 which is a desensitizer for surface-sensitized silver halide emulsions. In one aspect, this invention relates to a process for forming negative photographic images comprising (1) imagewise-exposing a silver halide emulsion which comprises silver halide grains containing metal dopants occluded therein and wherein said grains have adsorbed to the surface thereof a desensitizer or an electron-acceptor compound and (2) developing said exposed emulsion in an internal-image silver halide developer. Black-and-white and color diffusion transfer photographic elements employing the novel silver halide emulsions are also described.

This invention relates to improved silver halide emulsions. In one aspect, this invention relates to silver halide emulsions comprising unfogged, silver halide grains having metal dopants occluded therein and having adsorbed thereto desensitizing compounds which desensitize silver halide emulsions which have been only surface-sensitized. In another aspect, this invention relates to internal-image emulsions comprising internally sensitive, unfogged, silver halide grains which have absorbed thereto compounds which are generally classified as electron acceptors or desensitizers. In still another aspect, this invention relates to an improved process for forming a negative image comprising (1) imagewise exposing a silver halide emulsion comprising silver halide grains which have metal dopants occluded therein and wherein said grains have absorbed to the surface thereof a desensitizer or electronaccepting compound and (2) developing said exposed emulsion in an internal-image solvent developer.

It is known in the prior art to sensitize spectrally silver halide emulsions. However, use of organic dyes for spectral sensitization of silver halide emulsions has somewhat been restricted by the groupings on the dyes or within supersensitizing combinations which strongly densensitize the blue speed of the silver halide emulsion. Thus, the efiiciency of the silver halide system for recording image exposure is substantially reduced. Moreover, many compounds which are very useful as color developers, antifoggants, brighteners and the like could not be used effectively since this strongly reduces the blue speed of a silver halide emulsion. Therefore, improved emulsion systems are desirable wherein compounds can be used which are known to desensitize silver halide emulsions which have been only surface-sensitized.

We have now found that compounds which normally desensitize surface-sensitive silver halide emulsions with respect to blue-speed sensitivity can be used to provide improved photographic properties in internal-image emulsions containing metal dopants occluded therein without the accompanying loss in blue-speed sensitivity when developed in an internal-image silver halide developer. In one aspect, compounds which are generally known in the are as electron-accepting compounds, such as in directpositive emulsion literature, can now be used with unfogged, internal-image, silver halide emulsions to provide silver halide systems having improved spectral sensitivity. In another aspect, compounds which are known to be useful as color developers, azo dyes in dye bleach systems, antifoggants and conversion compounds to provide color images can now be used in combination with silver halide grains with high internal sensitivity to provide an improved system with improved blue-speed sensitivity.

In one preferred embodiment, this invention relates to internal-image emulsions containing unfogged silver halide grains and electron-accepting compounds which have a cathodic halfwave potential which is more positive than 1.0.

Another preferred embodiment relates to internal-image silver halide emulsions comprising unfogged silver halide grains and a tetrazolium salt.

Another preferred embodiment of this invention relates to an internal-image emulsion containing unfogged silver halide grains and a compound which reduces the bluespeed sensitivity of a control sulfur and gold surfacesensitized, silver bromoiodide emulsion (6 mole percent iodide) having an average grain size of about 1 micron at least 0.3 log B when developed in a surface developer such as Kodak Developer D-l9.

Another preferred embodiment of this invention relates to photographic film units containing at least one metal-doped silver halide grain emulsion containing a Schilf base of a color developer and a coupler which forms a dye which can be transferred to an image-receiving layer after exposure and contact with a processing composition.

Generally, the desensitizers or electron acceptors useful in the emulsion combinations of this invention are those compounds having a reduction potential or cathodic halfwave potential (B more positive than l.0, i.e., -0.40, -0.2 and the like, which do not have a primary adsorption peak in the infrared regions of the electromagnetic spectrum. In certain preferred embodiments, they are also characterized as not having a primary absorption peak in the visible region of the electromagnetic spectrum.

The cathodic measurements can be made with a 1X10" molar solution of the electron acceptor in a solvent, for example, methanol which is 0.05 molar in lithium chloride using a dropping mercury electrode with the polarographic halfwave potential for the most positive cathodic wave being designated E In the measurement, the reference electrode can be an aqueous silversilver chloride (saturated potassium chloride) electrode at 20 C. Electrochemical measurements of this type are known in the art and are described in New Instrumental Methods in Electrochernistry, by Delahay, Interscience Publishers, New York, N.Y., 1954; Polarography, by Kolthoff and Lingane, 2nd edition, Interscience Publishers, 'New York, N.Y., 1952; Analytical Chemistry, 36, 2426 (1964), by Elving; and Analytical Chemistry, 30, 1576 (1958), by Adams. Plus and minus signs are according to IUPAC (International Union of Pure and Applied Chemistry) Stockholm Convention, 1953.

In a preferred embodiment of this invention, the desensitizers are methine dyes, generally referred to as monomethine and/or polymethine dyes. Generally, these methine dyes include those which are useful in direct positive silver halide emulsions as electron acceptors.

In certain preferred embodiments, the useful polymethine dyes of this invention can be characterized as containing at least one desensitizing nucleus. As used herein and in the appended claims, desensitizing nucleus refers to those nuclei which, when converted in a symmetrical carbocyanine dye and added to a gelatin silver chlorobromide emulsion containing 40 mole percent chloride and 60 mole percent bromide, at a concentration of from 0.01 to 0.2 gram dye per mole of silver, cause by electron trapping at least about an 80 percent loss in the blue speed of the emulsion when sen sitometrically exposed and developed 3 minutes in Kodak Developer D-l9 at room temperature. Advantageously, the densensitizing nuclei are those which, when converted to a symmetrical carbocyanine dye and tested as just described, essentially completely desensitize the test emulsion to blue radiation (i.e., cause a loss of more than about 90 to 95 percent of speed to blue radiation).

An especially useful class of electron-accepting compounds which can be used in the photographic silver halide emulsions of this invention is cyanine dyes, particularly imidazoquinoxaline dyes, such as described in Brooker et al., US. Pat. 3,431,111 issued Mar. 4, 1969. Very good results are obtained with cyanine dyes containing an indole nucleus aromatically substituted in the 2 position, i.e., a cyanine dye containing a Z-aromatically substituted indole nucleus such as disclosed in U.S. Pat. 3,314,796 issued Apr. 18, 1967. One useful class of spectral-sensitizing, electron acceptors in the bis (1- alkyl 2 phenylindole 3)trimethine cyanine described by Coenen at al., US. Pat. 2,930,694 issued Mar. 29, 1960. Another useful class of dimethine cyanine dyes of this type is described in British Pat. 970,601.

Still other classes of useful spectral-sensitizing electron acceptors are the cyanine and merocyanine dyes in which at least one nucleus and preferably two nuclei contain desensitizing substituents such as N e.g., 3,3-diethyl- 6,6'-dinitrothiacarbocyanine chloride, as shown in British Pat. 723,019.

The electron acceptors or desensitizers can be used in the photographic silver halide emulsions of this invention in widely varying concentrations. However, such compounds are preferably employed at concentrations in the range of about 100 milligrams to about 2 grams of the compound per mole of silver halide. Specific examples of suitable polymethine electron acceptors include the following:

( 1 l,1-dimethyl-2,2-diphenyl-3,3'-indolocarbocyanine bromide (2) 2,2'-di-p-methoxyphenyl-1,1'-dimethyl-3,3'-indolocarbocyanine bromide l OMB M90 (3) 1,l'-dimethyl-2,2',8-triphenyl-3,3'-indolocarbocyanine perchlorate Ph 69 f (4) 1, 1','3,3'-tetraethylimidazo[4,5-b] quinoxalinocarbocy- :anine chloride pinacryptol yellow,

5-m-nitrobenzylidenerhodanine,

3ethyl-S-m-nitrobenzyldenerhodanine,

3-ethyl-5- (2,4-dinitrobenzylidene) rhodanine,

5-o-nitrobenzylidene-3-phenylrh0danine,

1',3-diethyl-6-nitrothia-2'-cyanine iodide,

4-nitro-6-chlorobenzotriazole,

3,3'-diethyl-6,6-dinit1'o-9-phenylthiacarbocyanine iodide,

2-(p-dirnethylaminophenyliminomethyl)benzothiazole ethoethyl sulfate,

crystal violet,

3,3'-diethyl-6,6'-dinitrothiacarbocyanine ethyl sulfate,

1',3-diethyl-6-nitrothia-2-cyanine iodide,

1,3-diamino-5-methylpheuazinium chloride,

4-nitro-6-chlorobenzotriazole,

3,3 -di-p-nitrobenzylthiacarbocyanine bromide,

3,3'-di-p-nitro-phenylthiacarbocyanine iodide,

3,3 -di-o-nitrophenylthiacarbocyanine perchlorate,

3,3-dimethyl-9-trifluoromethylthiacarbocyanine iodide,

9-(2,4-dinitrophenylmercapto)-3,3'-diethylthiacarbocyanine iodide,

bis(4,6-diphenylpyryl-2)trimethincyaniue perchlorate,

anhydro-Z-p-dimethylaminophenyliminomethyl-tS-nitro- 3- (4-sulfobutyl)benzothiazolium hydroxide,

1-(Z-benzothiazolyl)-2-(p-dimethylaminostyryl)-4,6-diphenylpyridinium iodide,

2,3,S-triphenyl-2H-tetrazolium chloride,

2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-tetrazolium chloride,

1-methyl-8-nitroquinolinium methyl sulfate,

3,6bis [4- 3-ethyl-2-benzothiazolinylidene -2-butenylidene]-1,2,4,S-cyclohexanetetrone and the like.

The organic compound useful herein may also serve as spectral sensitizers in the visible region of the electromagnetic spectrum since they do not strongly desensitize the doped emulsions of this invention. An especially useful class of spectral-sensitizing electron acceptor is trimethine cyanine dye containing a 2-aromatically substituted indole nucleus attached by the 3-carbon atom thereof to the methine chain. Dyes of this type are described by Coenen et al in US. Pat. 2,930,694 issued Mar. 29, 1960, and British Pat. 970,601 (and corresponding Belgian Pat. 630,911). A preferred class of spectrally sensitizing electron acceptors is dye containing an imidazo[4,5-b]quinoxalinium salt moiety, such as disclosed in Brooker and Van Iare, Belgian Pat. 660,253 issued Mar. 15, 1965. In these dyes, the imidazo[4,5-b] quinoxaline nucleus is attached, through the Z-carbon atom thereof, to the methine chain.

Another class of highly useful polymethine dyes is that having the following formula:

wherein R R and R each represents an alkyl group, such as methyl, ethyl, propyl or butyl, or an aryl group such as phenyl; X represents an anion, such as chloride, iodide, bromide, p-toluene sulfonate, methyl sulfate, perchlorate, thiocyanate, sulfonate, bromide, etc., and Q represents the atoms necessary to complete a nucleus to form a trimethine cyanine dye, such as a fi-nitrobenzothiazole nucleus, an imidazo[4,5-b]quinoxaline nucleus or a pyrrolo[2,3-b]pyridene nucleus, e.g.,

wherein X has the meaning given above; A represents an aryl substituent, such as phenyl; R and R each represents an alkyl radical, e.g., an alkyl substituent (including substituted alkyl) and preferably containing from about 1 to 8 carbon atoms, such as methyl, ethyl, propyl, butyl or octyl, or sulfoalkyl such as sulfopropyl or sulfobutyl, sulfatoalkyl such as sulfato-propyl or sulfatobutyl, or carboxyalkyl such as carboxyethyl or carboxybutyl; and Y represents a substituent selected from the group consisting of a hydrogen atom, an aryl group, such as phenyl, and alkyl (e.g., methyl, ethyl, propyl or butyl) or alkoxy (e.g., methoxy, ethoxy or propoxy) substituted phenyl groups, or a heterocyclic group, such as thiophene radical.

Symmetrical imidazo [4,5-b] quinoxaline trimethine cyanine dyes, wherein each nucleus is attached through the 2-carbon atom thereof to the methine chain, are useful in the practice of this invention. Typical of such dyes are those having the following general formula:

Formula 3 7 wherein X has the meaning given above; and R R R and R each represents a substituent such as alkyl, e.g., methyl, ethyl, propyl or butyl. Reference is made to Brooker and VanLare, Belgian Pat. 660,253 issued Mar. 15, 1 965, for other classes and specific examples of dyes containing an imidazo[4,5-b]quinoxaline nucleus which are useful herein.

Another useful class of desensitizers which can be used in accordance with this invention is the tetrazolium salts. These compounds can be incorporated in silver halide emulsion to provide color images such as disclosed in British Pat. 908,299, U.S. Pat. 3,185,567 issued May 25, 1965, and U.S. Pat. 3,503,741 issued Mar. 31, 1970, which are incorporated herein by reference. The tetrazolium salts generally desensitize the silver halide emulsions; thus, a long exposure is required as the efiiciency of the system is generally quite low. However, the combination of tetrazolium salts with the metal-doped silver halide grain emulsions of this invention provides a much more efiicient system as the desensitization effects of the tetrazolium salts are substantially obviated.

In the past, antifoggants which had a cathodic halfwave potential more positive than -1.0 were generally avoided since the efliciency of the silver halide system was substantially reduced because of desensitization. However, these compounds which have a cathodic halfwave potential more positive than 1.0 can now be used With the metal-doped silver halide grain emulsions of this invention since the inherent desensitization effects do not substantially lower the etficiency of these systems.

In one embodiment, the present invention allows one to incorporate color developers and/or Schifi bases thereof, such as those disclosed in French Pat. 983,022, British Pat. 632,836, British Pat. 1,066,352 and the like into unfogged silver halide emulsions. Compounds of this type were generally not used in negative-forming emulsions since they caused strong desensitization as disclosed in Belgian Pat. 700,717. While the color developer itself may not have an E more positive than 1.0, the oxidation products formed when they are incorporated in silver halide emulsions generally have an B more positive than --1.0. In one preferred embodiment, the alkyloxy Schiff bases or N-ethyl-N-hydroxyethyl-p-phenylenediamine are added to the emulsions of this invention.

Generally, the internal-image emulsions of our invention comprise those which, when examined according to normal photographic testing techniques by coating a test portion of the emulsion on a transparent support, exposing to a light-intensity scale for a fixed time between 1 10- and 1 second, bleaching 5 minutes in a 0.3% potassium ferricyanide solution at 65 F. and developing for about 5 minutes at 65 F. in Developer B below (an internal-type developer), have a sensitivity, measured at a density of 0.1 above fog, greater than the sensitivity of an identical test portion which has been exposed in the same way and developed for 6 minutes at 68 F. in Developer A below (a surface-type developer). Generally, the internal-image emulsions have a predominant amount of sensitivity internal to the grain and preferably have a ratio of total sensitivity to surface sensitivity of greater than 10. Developer A is the usual type of surface-image developer and Developer B is an internal developer having high silver halide solvent activity.

Developer A Water to 1 liter.

The internal-image emulsions which are useful according to this invention are those which contain grains having a metal dopant occluded therein. The metal dopants can be occluded within the grain, for example, by precipitating in the presence of foreign metal ions (i.e., other than silver ions). The metal dopants can be introduced by chemically sensitizing a core of a silver halide grain to form a metal or metal salt thereon and then forming a shell or outer region on the core occluding the chemically sensitized site within the grain, etc. Typical useful silver halide emulsions containing grains having metal dopants occluded therein can be prepared by the procedures disclosed in Porter et al., U.S. Pat. 3,206,313 issued Sept. 14, 1965; Porter et al., U.S. Pat. 3,317,322 issued May 2, 1967; Berriman, U.S. Pat. 3,367,778 issued Feb. 6, 1968, omitting the surface fogging procedure; British Pat. 1,027,146; Bacon et al., U.S. Pat. 3,447,927 issued June 3, 1969; Bacon et al., U.S. Ser. No. 629,090 filed Apr. 7, 1967, now U.S. Pat. 3,531,291; Berrirnan, British lPat. 1,151,782; McBride, U.S. Pat. 3,271,157 issued Sept. 6, 1966; and the like.

The silver halides used in the present invention are unfogged. Such emulsions contain no substantial developable or visible surface latent image. The silver halide emulsions may be coarseor fine-grain emulsions and can be prepared by many of the procedures available for making silver halide emulsions, e.g., singlejet emulsion procedures, double-jet emulsion procedures, ammonical emulsions, thiocyanate and/or thioether ripened emulsions, emulsions prepared using increased flow rates as disclosed in U.S. Ser. No. 11,838 by Wilgus filed Feb. 16, 1970, hot nucleation procedures as disclosed in U.S. Ser. 31,351 by Musliner, filed Apr. 23, 1970, and the like.

In a preferred embodiment, the silver halide grains are formed in the presence of foreign metal ions and preferably polyvalent metal ions. Generally, when the grains are formed in an aqueous medium, the silver halide grains are formed in the presence of the water-soluble salts of the respective metal, preferably in an acidic medium. Typical useful polyvalent metal ions include trivalent metal ions such as antimony, bismuth, arsenic, gold, iridium, rhodium and the like and tetravalent metal ion such as platinum, osmium, iridium and the like. In highly preferred embodiments, the grains are formed in the presence of bismuth, lead or iridium ions. Generally, the silver halide grains contain at least and preferably at least 10* mole percent dopant based on silver halide.

Photographic elements prepared according to this invention can be processed by various methods which utilize internal-image silver halide developing compositions containing silver halide solvents and developing agents such a hydroquinones, catechols, aminophenols, 3-pyrazoliclones, phenylenediamines, ascorbic acid derivatives, hydroxylarnines, hydrazines, reductones and the like, including procedures such as Web processing as described in U.S. Pat. 3,179,517 by Tregillus et al.; stabilization processing as described in Russell et al., Stabilization Processing of Films and Papers, PSA Journal, vol. 16B, August 1950; monobath processing as described in Levy, Combined Development and Fixation of Photographic Images With Monobaths, Phot. Sci. and Eng, vol. 2, No. 3, October 1958, and Barnes et al., U.S. Pat. 3,392,019. If desired, the photographic elements of this invention can be processed in hardening developers such as those described in U.S. Pat. 3,232,761 by Allen et al.; in roller transport processors such as those described in U.S. Pat. 3,025,779 by Russell et al.; or by surface application processing as described in Example 3 of U.S. Pat. 3,418,132 by Kitze.

In addition, photographic elements of this invention having an incorporated Schiff base of a color developer can be employed in color diffusion transfer film units such as those described in U.S. Pats. 3,227,550, 3,227,551 and 3,227,552 in which an image-receiving element is superposed over the photographic element after exposure thereof, the film unit also containing a rupturable container having therein an alkaline processing composion which is spread between the exposed photographic element and image-receiving element by pressure-applying members in a camera. After development, the image-receiving element is then stripped away from the photographic element to reveal a positive transferred image. The photographic elements of this invention having an incorporated Schiff base of a color developer can also be employed in integral color diffusion transfer film units such as those described in Barr et al., Ser. No. 027,991 filed Apr. 13, 1970, and Cole, Ser. No. 027,990 filed Apr. 13, 1970 now abandoned. In such integral diffusion transfer film units,

the dye image-receiving layer is located between the support and the silver halide emulsion layer or layers, no timing of development or stripping of the image-receiving layer from the photographic element is required and the transferred positive image is viewable through a trans parent support. To obtain the transfer image in the abovedescribed color diffusion transfer systems, the silver halide emulsion has contiguous thereto a nondiifusible coupler capable of reacting with the oxidized color developing agent, such as a p-phenylenediamine, to form a diffusible dye. Such couplers are described in more detail in the above-mentioned patents and patent applications. Of course, to obtain a multicolor transfer image, blue-sensitive, green-sensitive and red-sensitive silver halide emulsions are employed in the photographic element, each said emulsion having contiguous thereto a nonditfusible coupler capable of reacting with oxidized color developing agents to form a yellow dye, a magneta dye and a cyan dye, respectively.

The invention can be further illustrated by the following examples.

EXAMPLE 1 A silver halide emulsion containing grains having iridiumoccluded therein is prepared as described in Berriman, U.S. Pat. 3,367,778, except the grains are not surfacefogged. The emulsion coating is prepared to the following specification:

0.2g. cubic silver bromoiodide grains 2.3 kg. of emulsion/mole of silver 80.0 g. of gel/ mole of silver pAg of 8.9

To 3l-g. samples of the emulsion are added 75 ml. of 5% gelatin, 1.0 ml. of a 7 /z% saponin solution and 0.5 ml. of a 10% formaldehyde solution. To 10 m1. of a sample is added a dye, identified below, in a 0.1% methanolic solution and a 5% gelatin solution to make a total of 15 ml. The mixture is held for 15 minutes at 40 C. and coated at .004" thickness on a subbed cellulose acetate support.

After drying, the coatings are exposed in a wedge spectograph for /2 second at 1.0 mm. with the following results:

NOTE: Dye I=1, 3-diethyl-1-methyl-2'-phenylimidazo {4, 5-b] quinoxalino-3-indoloearbocyanine iodide (E is -0.64).

The excellent spectral sensitization from Dye I is unexpected because it is a powerful desensitizer in normal negative systems.

EXAMPLE 2 This example demonstrates the improved speed properties which can be obtained with internal-image emulsions containing desensitizer-type compounds compared with surface-sensitive emulsions.

The surface-sensitive emulsion, a bromoiodide emulsion (6.0 mole percent iodide) having an average grain size of 1.0 micron, is chemically sensitized at the surface of the grains by adding 4.4 mg. of sodium thiosulfate/ silver mole and 1.8 mg. of potassium chloroaurate/silver mole and heating until optimum sensitivity is obtained.

The internally sensitive metal-doped emulsion, a bromoiodide emulsion (2.5 mole percent iodide) having an average grain size of 0.2 micron, is prepared by adding 106 mg. of potassium hexachloroiridate per mole of silver to a gelatin solution prior to the precipitation of the silver halide.

To separate portions of the above washed emulsions are added the compounds at the concentrations described in the following table. All of these compounds have an E,

more positive than 1.0. The samples are then coated on a film support and exposed & second and 5 seconds respectively on a Bausch and Lomb spectrograph. The surface-sensitive emulsion samples are developed for 8 minutes in Kodak Developer D-19 (a surface developer) while the internal-sensitive emulsion samples are developed for 8 minutes in Kodak D-l9 containing 0.5 g. of potassium iodide/ liter (an internal developer).

The intrinsic photographic speeds are recorded in the following table:

Surface-sensitive Internal-sensitive emulsion emulsion Relative Relative Compound G./mole speed G./mole speed None (control) 100 100 A 3 30 67 30 60 53 60 l. 2 35 60 7 1. 2 67 1. 2 6 2. 4 58 2. 4 4 4. 8 63 003 23 006 89 009 8 018 82 03 06 78 003 55 006 105 009 23 018 95 03 5 06 89 45 4 90 58 90 2 1. 8 55 1. 8 3. 6 58 03 23 06 95 09 6 18 100 3 6 89 09 71 18 155 3 55 6 170 9 33 1. 8 155 A=4-nitro-6ehlorobenzotriazole. B =5-chloro-6-nitrobenzotriazole. A C 1, 1-di-n-butyl-4, 4-bipyridiniu1n dibronude. D 2, 2-azopyridine.

E=2, 3, 5-tripheuyl-2H-tetrazolium chloride. I i I F=1, 3-diethyl-1'-methyl-2'-phenylimidazo [4, 5-1)] qumoxohno-El mdoar ocyanine iodide (U.S. Patent 3,314,796). G 4-amino4-etl1yl-N-B-hydroxyethylamhne sulfate.

Compound G is a color developer which densensitizes a surface-sensitized emulsion as a result of the oxidation product formed when it is incorporated in an emulsion. This oxidation product has an E more positive than 1.0.

Similar improvements in speed with the metal-doped emulsion are obtained when the following compounds, generally referred to as desensitizers or electron acceptors, are incorporated in the emulsion.

2, 6-bis 4-ethylphenyl 4-4-N- (amyloxyphenyl) carbocyanne perchlorate (E is -0.39)

1-(p-dimethylaminophenylcinnamylidene-Z,3-diphenylpyrrocolinium perchlorate (E is 0.21)

1, l '-dimethyl-2,2'-diphenyl-3 ,3 '-indolocarbocyanine bromide (E is 0.20)

1,3-diethyl-2- [2- (9-methyl-3-carbazolyl) vinyl] imidazo [4,5-b] pyrido [2,3-e] pyrazinium perchlorate (E is 0.26)

2,2'-di-p-carboxyphenyl-3,3'-dimethyl-l ,1'-pyrrocolocarbocyanine perchlorate (E is 0.39)

S-N-nitrobenzylidene rhodanine (E is 035) 5, 5 '-dichloro-3 ,3 -diethyl-6,6-dinitrothiacarbocyanine iodide (E is 0.34)

6,7-dichloro-2- (4-dimethylarniuostyryl)-1,3-diphenylimidazo- [4, S-b] quinoxaliniurn paratoluene sulfonate (\E is 0.32)

1,3-diethyl-2- [2- (3 ,4-dimethyl- 1-phenyl-4-pyrazolyl) vinyl] imidazo [4,5 b] quinoxalinium iodide (E is 0.45)

6,6',7,7'-tetrach1oro-1,1',3,3 '-tetraphenylimidazo [4,5-b]

quinoxalinocarbocyanine paratoluene sulfonate (E is 0.45)

5,5'-dichloro-3,3-diethyl-6,6'-dinitrothiacarhocyanine iodide (E is 0.46)

3-ethy1-5-[ l-ethyl-4,9-dioxo-3-phenylnaphth[2,31-imidazolylidene)ethylidene]rhodanine (E is 0.4l)

10 1,1'-diethyl-6,6'-dinitro-2,2'-cyanine iodide (E is -O.55) 4,6-di(4-chlorophenyl)-2-(4-nitrostyryl)-1-(4-phenylaziophenyl)pyridinium iodide (E is 0.55) 1'-ethyl-lmethyl-Z-phenyl-4'-p-nitrophenyl-3-indolo-5'- tetrazolocarbocyanine iodide (E is 0.50)

Phenosafranine (E is 0.54)

2,2'-diethyl-7,8-diaz0thiacarbocyanine iodide (E is 0.61)

6,7 dichloro- 1, 1,3,3',3 '-pentamethyllH-imidazo [4,5 b]

quinoxalinopyrrolo [2, 3-b] pyridocarbocyanine perchlorate (E is 0.64)

6,7-dichloro-2- [2- 1methyl-Z-phenyl-3-indolyl) vinyl] 1,3-diphenylirnidazo[4,5-b] quinoxalinium paratoluene sulfonate (E is 0.61)

Pinacryptol yellow (E is 0.66)

l,1',3 ,3 '-tetraethylirnidazo [4,5-b] quinoxalinocarbocyanine chloride (E is 0.79)

1-methyl-3-[ (2-methyl-S-oxo-3-phenyl-3isoxazolin-4-y1)- methylene]-2-phenyl-3H-indolium iodide (E is 0.75)

3 ,3 '-diethyl-1 l-methylthiazolo [4,5 b] quinocarbocyanine bromide (E is 0.72)

Crystal violet (E is -0.77)

l,3-diallyl-1,3-diethyl-(2-imidazo[4,5-b]pyrido[2,3-c]- pyrazino) 2-imidazo [4, 5-b quinoxalinocarbocyanine perchlorate (E is 0.81)

5[ (3ethyl-2-benzothiazolinylidene)ethy1idene]-1-methyl- 3-(4-nitropenyl)2-thiohydantoin (E is 0.80)

1, 1,3-triethylimidazo [4,5-b] quinoxalino-2'-carbocyanine iodide (E is 0.89)

6-dimethylamino-1'-3,S-trimethyl-1-phenyl-4-pyrazolo- '2'-carbocyanine iodide (E is -'0.88)

1, l ',3,3'-tetraethylimidazo [4,5-b] quinoxalinocyanine perchlorate (E is 0.90)

1,1'-methylene-2,2'-cyanine iodide (E is 0.90)

Anhydro-S ,5 '-dichloro-3,3-di (4-sulfobutyl) thiacarbocyanine hydroxide, sodium salt (E is 0.99)

EXAMPLE 3 The comparative samples illustrate advantages internalsensitive emulsions have over surface-sensitive emulsions when such emulsions contain tetrazolium salts. Tetrazolium salts have the utility of converting photographic metal images to formazan dye images as described in Bissonette et al., British Pat. 908,299, and U.S. Pat. No. 3,185,567 issued May 25, 1965.

A description of the emulsion preparation and their tabulated results follow:

Emulsion A is prepared by adding aqueous silver nitrate and a mixture of potassium bromide and potassium iodide simultaneously to a gelatin solution containing 106 mg. of potassium chloroiridate/ silver mole.

Emulsion B is prepared similar to Emulsion A, except potassium chloroiridate is omitted.

The emulsions, 0.2 micron in diameter, are then washed as described in Yutzy, U.S. Pat. 2,614,928. Emulsion B is chemically sensitized by adding 3.3 mg. of sodium thiosulfate/silver mole and 6.6 mg. of potassium chloroaurate/ silver mole and heated for 28 minutes at 65 C. The emulsions are then coated on a polyethylene terephthalate film support at mg. of silver/ft. and exposed for & second on a Bausch and Lomb Spectrograph. Both the internal-image emulsion and the surface-image emulsion are developed in an internal developing solution of the Distilled water to 1 liter.

Addenda Rel.

Emulsion (mgJAg mole) speed 7 Fog 1 I-2,3,5-tripheny1-2H-tetrazol1um chloride.

The above table shows that tetrazolium salts desensitize surface latent image emulsions but do not desensitize internal latent image emulsions.

EXAMPLE 4 An internal-image emulsion, a bromiodide emulison (2.5 mole percent iodide) having an average grain size of 0.2 micron, is prepared by adding 106 mg. of potassium hexachloroiridate/mole of silver to the gelatin solution prior to the precipitation of the silver halide. To a portion of the emulsion are added 100 mg. of 1,3-diethyl-1- methyl 2' phenylimidazo[4,5-b] quinoxolino-3-indolocarbocyanine iodide per silver mole, described in British Pat. 1,186,716, Dye A, as an electron acceptor. The emulsion is then coated at 100 mg. silver/ft. on a film support and exposed to 20 foot candles of illumination for 5 seconds through a line image. The coating is then rolled in contact with a receiver and pod containing a viscous processing composition of the type described in U.S. Pat. 2,823,122. After seconds, the receiver is separated from the film support and on the receiving layer is noticed a high-quality positive image.

Similar results are noticed when the electron-accepting dye is substituted with 200 mg. of the dye 3-ethyl-5-[(2- ethyl 1(2) benzothiazylidene)hexadienylidene]rhodamine per silver mole.

Similar results are obtained when the emulsions used in combination with the electron acceptors contain grains having osmium ions, rhodium ions and bismuth ions occluded therein.

EXAMPLE 5-A To 10 g. of 0.2 cubic, silver bromoiodide emulsion prepared with an iridium dopant as described by Berriman in U.S. Pat. 3,367,778, but without fogging of the surface, are added 10 m1. of a coupler dispersion prepared by dissolving 0.8 g. of the coupler [1-phenyl-3 (3,5-disulfobenzamido) 4-(4-octadecyloxyphenylazo)-5-pyrazolone] similar to coupler B of U.S. Pat. 2,983,608 in a mixture of 6 ml. Alkanol B.

in 50 ml. of hot ethyl alcohol saturated with sulfur dioxide is dissolved 1.0 g. of the following color developer- Schifi base of octadecyloxyaldehyde:

H502 CHaCHzOH then added to 50 m1. of a 10% gelatin solution. To the above coupler-containing emulsion is added 20 ml. oi the color developerSchifi base solution.

To the emulsion-coupler-developer mixture is added 1 ml. of a 7 /2 aqueous saponin solution and 0.2 m1. of a 10% aqueous formaldehyde solution.

The final mixture is coated 0.006" wet thickness on subbed celluose acetate support.

The resulting coating is exposed in a modified Bausch and Lomb Spectrograph for 1 second at 1.0 mm. slit width, then developed in an Elon-hydroquinone internal-image developer containing 1 g./l. of potassium iodide. A wedge spectrogram results which shows the coating has spectral sensitivity from 340 nm. to 620 nm., whereas a similar coating of the emulsion without the color developer-Schifi base has spectral sensitivity from 340-510 nm.

EXAMPLE 5 B It is found that the coating described in Example 5-A can be used to form excellent magenta-dye transfer images to suitable mordant receiving layers. A representative dye mordant layer is prepared by adding 4.3 cc. of a 35% solution of Catanac SP (an organic cationic compound sold by American Cyanamid Co.) to ml. of a 2% gelatin solution containing 1 ml. of 7 /z% aqueous saponin solution and 0.3 ml. of a 10% formaldehyde solution. Coatings are made on polyethylene-coated paper at a wet thickness of 0.004.

To make the color transfer images, the emulsion coating described in Example 5-A is exposed for 5 seconds in a Bausch and Lomb Spectrograph, then immersed for 15 seconds in the following alkali activator;

ml. distilled water 10 ml. of a 2.5 molar sodium hydroxide solution 0.25 g. of potassium iodide The emulsion coating is then rolled in contact with the Catanac SP mordant layer for 1 minute. After stripping the two layers apart, a good magenta-dye image is formed in the mordant layer in areas of exposure of the negative and again spectral sensitization is achieved out to 620 nm. In this example, the alkaline activator serves to liberate the color developer which, in turn, develops the silver halide emulsion, thus becoming oxidized. The oxidized developer then reacts with the coupler to form a magenta dye which transfers to the receiver.

EXAMPLE 6- In certain preferred embodiments, we have found that dyes having high extinction coefiicients can be used in combination with the doped emulsions of this invention to provide improved photographic properties. In one highly preferred embodiment, imidazoquinoxaline dyes are used which have high extinction coeflicients.

A silver bromide emulsion is prepared by mixing simultaneously over a period of 28 minutes at a temperature of 70C. equal molar portions of silver nitrate and sodium bromide, using an automatic proportional controller to introduce the liquids into the precipitation vessel. Upon completion of the precipitation, silver halide grains of about 0.5 micron result. The silver bromide grains are chemically sensitized by adding 1.7 mg. of sodium thiosulfate per mole of silver and 2.5 mg. of potassium chloroaurate per mole of silver, followed by heating for 30 minutes at 70 C. The chemically sensitized grains are then further grown in the same precipitation environment as the first precipitation for an additional 28 minutes such that the final crystal structure results in grains of 0.8 micron in size.

To separate samples of the emulsion are added 100 mg., 500 mg. and 900 mg. of 1,1,3,3'-tetraethylimidazo [4,5-b] quinoxalino carbocyanine chloride per mole of silver (extinction coeflicient is 30.3)(10 and E is 0.83). The samples are coated imagewise, exposed and developed in 13 the developer as in Example 3. The observed results indicate substantially no blue-speed desensitization in any of the samples and also no stain is observed in the processed coatings.

EXAMPLE 7 A radiation-sensitive gelatin silver chlorobromide photographic emulsion is prepared in the presence of bismuth ions as described in Example 18 of U.S. Pat. 3,447,927. A desensitizing dye, 1,3 diethyl-1'-methyl-2'-phenylimidazo[4,5-b]quinoxolino-3'-indolocarbocyanine iodide (E is --0.64), is added to portions of the emulsion at 250 mg. and 400 mg. per mole of silver. The emulsion samples are then coated at 60 mg. Ag/ft. in admixture with 34 g./silver mole of dithiourazole methyl vinyl ketone adduct as described in Wise et al., U.S. Ser. No. 816,867 filed Apr. 4, 1969 corresponding to Belgian Pat. 745,908, now U.S. Patent 3,615,618.

Exposure Relative speed B MB It is apparent that this dye which is a desensitizer for most silver halide emulsions will spectrally sensitize this doped emulsion without concomitant blue-speed desensitization.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention.

We claim:

1. In a process for forming a negative image, the improvement comprising (1) imagewise exposing a photographic element comprising a support having thereon at least one layer containing an internal-image, silver halide emulsion comprising unfogged silver halide grains having a ratio of total sensitivity to surface sensitivity of greater than 10 and having a foreign metal ion dopant selected from the group consisting of trivalent metal ion dopants and tetravalent metal ion dopants occluded therein and a desensitizer compound having a cathodic halfwave potential more positive 1.0 and (2) developing said exposed element in an internal-image, silver halide developer.

2. A photographic element comprising a support having thereon at least one layer containing a silver halide emulsion comprising unfogged silver halide grains having a ratio of total sensitivity to surface sensitivity of greater than 10 and which have a foreign metal ion dopant selected from the group consisting of trivalent metal ion dopants and tetravalent metal ion dopants occluded therein and have adsorbed to the surface thereof a concentration of a desensitizer compound having a cathodic halfwave potential more positive than 1.0 above the concentration which would produce a loss in blue sensitivity in a control sulfur and gold surface-sensitized silver bromoiodide emulsion, containing 6 mole percent iodide, having an average grain size of about 1 micron, of at least 0.3 log E when developed in Kodak Developer D-19 having the composition:

G. N-methyl-p-aminophenol sulfate 2.0 Sodium sulphite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrated 52.5 Potassium bromide 5.0

Water to 1 liter.

3. A photographic element according to claim 2 wherein said metal dopant is an iridium, bismuth or lead ion.

4. A photographic element according to claim 2 wherein said desensitizer compound is an organic spectral sensitizing dye which has a cathodic halfwavepotential more positive than 1.0.

5. A photographic element according to claim 4 wherein said desensitizer is a cyanine dye.

6. A photographic element according to claim 2 wherein said desensitizer is a polymethine dye.

7. The photographic element of claim 2 wherein said desensitizer is a Schitf base of a color developing agent.

8. The photographic element of claim 7 wherein said silver halide emulsion has contiguous thereto a coupler which is capable of reacting with said color developing agent after oxidation to form a diifusible dye.

9. The photographic element of claim 8 in combination with a dye image-receiving layer and a rupturable container containing an alkaline processing composition, said rupturable container being adapted to be positioned during processing so that a compressive force applied to it will effect a discharge of the containers contents within said photographic element.

10. The photographic element of claim 9 wherein said dye image-receiving layer is located between said support and said silver halide emulsion layer.

11. The photographic element of claim 9 wherein said dye image-receiving layer is coated on a separate support and is adapted to be superposed on said silver halide emulsion layer after exposure thereof.

12. In a silver halide emulsion comprising an electronacceptor compound having a cathodic halfwave potential more positive than -1.0, the improvement comprising unfogged silver halide grains having a ratio of total sensitivity to surface sensitivity of greater than 10 and which have a foreign metal ion dopant selected from the group consisting of trivalent metal ion dopants and tetravalent metal ion dopants occluded therein.

13. An emulsion according to claim 12 wherein said metal dopant is a polyvalent metal ion.

14. An emulsion according to claim 12 wherein said metal dopant comprises iridium ions, bismuth ions, osmium ions or mixtures thereof.

15. A photographic element comprising a support having thereon at least one layer containing an internal image silver halide emulsion comprising silver halide grains, the surface of said grains being free of intentional chemical sensitization, said grains having a foreign metal ion dopant selected from the group consisting of antimony, bismuth, rhodium, platinum, osmium, iridium and lead ions occluded therein, and on the surface of said grains a concentration of desensitizer compound consisting essentially of an organic spectral sensitizing dye having a cathodic halfwave potential more positive than -l.0, above the concentration which would produce a loss in blue sensitivity in a control sulfur and gold surface-sensitized silver bromoiodide emulsion, containing 6 mole percent iodide, having an average grain size of about 1 mi- 15 cron, of at least 0.3 log E when developed in Kodak Developer D-19 having the composition:

G. N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrated 52.5 Potassium bromide 5.0

Water to 1 liter.

16. In a process for forming a negative image, the improvement comprising (1) imagewise exposing a photographic element comprising a support having thereon at least one layer containing an internal-image, silver halide emulsion comprising unfogged silver halide grains, the surface of said grains being free of intentional chemical sensitization, said grains having a foreign metal ion dopant selected from the group consisting of antimony, bismuth, rhodium, platinum, osmium, iridium and lead ions occluded therein and on the surface of said grains a concentration of desensitizer compound consisting essentially of an organic spectral sensitizing dye having a cathodic halfwave potential more positive than 1.0, above the concentration which would produce a loss in blue sensitivity in a control sulfur and gold surface-sensitized silver bromoiodide emulsion, containing 6 mole per- 16 cent iodide, having an average grain size of about 1 micron, of at least 0.3 log B when developed in Kodak Developer D-19 having the composition:

G. N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, m-onohydrated 52.5 Potassium bromide 5.0

9/1965 Porter et al. 96-101 9/ 1970 Litzerman 96107 NORMAN G. TORCI-IIN, Primary Examiner R. E. FIGHTER, Assistant Examiner U.S. Cl. X.R. 

